The present invention relates to a novel safety device for vehicle tires, particularly for tubeless tires, which enables, in the case of a flat, the preservation of all the characteristics of the tire, in particular its adherence and the driving stability of the vehicle, over a relatively long distance of at least 50 km which can be travelled at a reasonably high speed of 50 km/h.
Safety devices for vehicle tires are known in the Prior Art and are constituted by a rubber lining, generally annular, arranged in the pneumatic space of the casing to the tire, which has the purpose of maintaining the beads of the tire against the edges of the rim and to limit the collapse of the tire in the case of a flat.
In particular, French Pat. No. 2,419,188 describes a toroidal insertion part which is composed:
of a toric core of cellular material or foam, particularly polyurethane or polyethylene, PA1 of a radially-wound tire cord around the toric core and preferably composed of steel cable, and PA1 of at least one support member for the load on the tire, formed by means of a tire cord, which is also composed preferably of a steel cable and which is wound circumferentially around the middle third of the outer surface of said toric core. PA1 in that its weight, its geometry and its rigidity, as well as the SHORE A hardness of the elastomer from which the toric ring of the device is composed, are defined with great accuracy as a function of all types of tubeless tires, from the passenger tire to the truck tire; PA1 in that it can be introduced into the tire not only by means of specially-designed machines for this purpose, but also manually, in accordance with certain features of the invention, which permits any recourse to special tooling to be avoided, thus simplifying the operations of mounting the safety device and reducing the cost; PA1 in that it ensures, both before and after the flat, a driving safety which is satisfactory without destabilization of the vehicle, in any driving conditions whatever, and PA1 in that its design is such that it renders practically impossible, after a puncture, the loss of the tread. PA1 a toric safety ring, particularly of elastomer or plastomer, whose cross-section has a symmetrical configuration, with respect to a longitudinal median plane, obtained by circumferentially forming an annular groove at the lower portion and at the upper portion of said ring particularly; PA1 at least one inextensible member circumferentially engirdling a portion of the upper surface of the toric ring; PA1 a predetermined amount of lubricant interposed between the safety device and the tire, wherein said safety device is characterised in that the dimensions of the toric safety ring are calculated so as to ensure a sufficient internal contact between the tire and the upper portion of the device, to limit the range of movement of the tire and to ensure the safety of driving under any driving conditions whatever, in the case of a flat, and to give the device a height calculated, with respect to the internal height of the tire, to avoid a considerable collapse of the tire, and the risk of loss of the tread of the latter, particularly in that: PA1 the width L' at the top of the ring is such that: EQU L-3e.ltoreq.L'.ltoreq.L-e, PA1 where PA1 the height H' of the device is such that: ##EQU2## where H=internal height of the tire, PA1 in that its rigidity R is such that: EQU 750 kg/cm.ltoreq.R.ltoreq.1050 kg/cm,
The preparation of this insertion part is done before its positioning in the tire.
When the tire is inflated, said insertion part has a substantially oval central and thick portion, comprised between the beads of the tire and two thin end portions extending along approximately half its sides, so that, in the deflated position, said central portion supports the tread of the tire and the corresponding load, whilst the lateral portions support these side walls.
A protection against deflation is also known (see French Pat. No. 2,396,664) constituted by an annular element of elastic material, in particular of natural or synthetic rubber, which has a symetrical cross section with respect to the longitudinal median plane, particularly of H shape, composed of two spaced facing side-walls and connected by an annular bridge (all around of which are arranged vents) which thus define annular grooves at the upper portion and at the lower portion of the annular element.
This elastic ring cooperates with an annular obturation bead, which is composed of a plurality of rigid obturation elements, freely articulated in the radial direction, and which is consequently not flexible laterally. This obturation bead is arranged in the groove formed at the lower portion of the ring so as to clamp these sides and the beads of the tire, thus rigidifying this ring.
However, these known safety devices have all the common disadvantage of unacceptably increasing the weight of the tire, on account of their cooperation with heavy reinforcement means, and the necessity of always requiring special tooling for their mounting.
In addition the minimum guaranteed distance that the tire can cover after puncture and the average speed at which it is possible to drive the vehicle under these conditions are not specified in the known publications; and in particular, the latter do not state physical parameters, particularly the weight, the bulk, and the rigidity of the safety devices, ensuring rolling, in the case of a flat, over a guaranteed minimum distance at a certain average speed.
In addition, the too great rigidity of the majority of known safety devices, due to the cooperation of elements of different nature, which renders difficult the checking of its optimum value for various uses, results in a destabilization of driving, whereas those of these devices which are of flexible material, particularly alveolar, do not permit the mastery, under all conditions of driving, of performance after puncture and can cause loss of the tread of the tire due to the fact that they do not ensure sufficient control of the collapse of the tire.
It is an object of the present invention to provide a safety device for vehicle tires which responds better to the necessities of practice than the devices intended for the same purpose known previously, particularly: